534 BULLETIN 100, UNITED STATES NATIONAL MUSEUM. 



e^ Costae spaced with 1 or more intercostal bands of pedicellariae ; 



rays, 15. 



f. Costae 45, feebly developed ; in addition to the large subambulacral 



spine (4 times the length of its plate), an aboral apophysial 



furrow spinelet, and 1 adoral, not so deep in furrow. 



Brisinga andamanica Alcock and Wood-Mason. 



f. Costae 30 to 35, mostly complete, prominent though compressed 



and narrow ; in addition to the large subambulacral spine (4.5 



consecutive plates in length), 1 minor aboral subambulacral 



spine, and sometimes au aboral apophysial- furrow spinelet 



/- , i+l+I i+I o+l+I\ „, • 1 u 



(formulas — or or j- The proximal eub- 



ambulcral spines are slightly modified, with a truncate tip. 



C rater ohrislnga ecermanni (Fisher), 



d'. Costae less than 30, alternating with 1 or more intercostal bands of 



pedicellariae. 



e\ Disk large with vertical edge ; rays 13, not very deciduous ; costae 



13 to 17, very salient ; spinelets of disk coarser ; adambulacral 



i+1 

 armature -^7— +7, the minor subambulacral spinelets being on 



furrow margin, and small major subambulacral spine 4 to 5 times 



length of plate Brisinga insularum Alcock and Wood-Mason. 



e'. Disk small with beveled margin; rays very deciduous; major sub- 

 ambulacral spine 2 to 2.5 times length of plate. 

 f. Rays 14, not very fragile ; costae about 20, close together on basal 

 ninth of ray, and not much more salient than the bands of 



i+l 

 felted pedicellariae; adambulacral armature -rn+I- 



Brisinga bcngalcnsis Alcock and Wood-Mason. 

 f. Rays 14 or 15. very fragile, slender; costae 20 to 30, very con- 

 torted, salient laterally, inconspicuous abactinally ; disk very 



i-f-o 

 thin, with a downy appearance; adambulcral armature -tt^+Z- 



Brisinga gunnii Alcock. 



/*. Rays 11, costae 20 ; adambulcral armature ^nry; ^^^ below. 



Astrostephane acanthogenys (Fisher). 

 c*. Most or all of the disk plates with a single spinelet; sometimes a few 

 near margin with 2 or 3. 

 d\ Rays more than 10; rays not especially fragile, though deciduous; 

 suboral spines large ; first pair of adambulcral plates and first pair 

 of marginal plates in each iuterbrachium joined by their lateral 

 faces, 

 e*. Costae generally opposite each adambulcral plate, hence close to- 

 gether, and without conspicuous bands of intercostal pedicellariae ; 

 a single series of papulae around the disk close to edge, 2 opposite 

 base of each ray. 

 f. Conspicuous costae 25 to 30, occupying proximal fifth of ray; 

 pedicellariae larger, the proximal serrate edge of each blade in- 

 conspicuous, semicircular ; articular surface of proximal am- 

 bulacral ossicles smaller; rays 16. Brisingenes mimica (Fisher). 

 f. Conspicuous costae about 40, occupying proximal fourth of ray; 

 pedicellariae smaller with the proximal serrate edge of each 

 blade relatively larger in proportion to total length of blade and 



